In the fifth episode of the third season of The Blacklist, the person on the list is #50, Arioch Cain.

Elizabeth Keen is targeted by Wendigo, a vigilante / bounty hunter who kills his victims out of his own sense of justice. It turns out someone called Arioch Cain has put a crowd-sourced bounty on Elizabeth's head.

Arioch Cain turns out to be

the widower of a victim of the OREA-bombing Elizabeth was framed for. His daughter was the one who put Elizabeth on the hit list.

Reddington already knew about Wendigo, claiming he was even better than himself. He informs the team about Wendigo, who has killed a number of fugitive criminals — dictators on the run and so on.
Wendigo seems like a typical black lister: unknown to the FBI, high profile victims.

But Wendigo wasn't on the black list, it was Arioch Cain, who was unknown to Reddington and only became relevant since Karakurt's attack.